1. Field of the Invention
The present invention relates to photographic processes for producing photographic elements. More particularly, the present invention is directed to photographic processes which produce photographic elements adapted to result in enhanced reproduction of both fine line and continuous tone images.
2. Description of the Prior Art
Photographic processes which produce the high contrast required for recording fine line copy are known, such as the processes which utilize commercially available microfilm. Microfilm typically comprises a photographic support having coated thereon one or more negative-working photographic silver halide emulsion layers. These emulsions are typically of high contrast (i.e., having a contrast greater than or equal to about 1.5) in order to satisfactorily record micro-image areas, such as fine line copy. These emulsions thereby provide adequate viewing and printing of micro-image information displayed on microfilm reader-printers.
Although the majority of the information recorded on microfilm is micro-image information, such as fine line copy, continuous tone and large area uniform tone (macro-image) information must also be copied. Unfortunately the high contrasts chosen for optimum micro-image recording are poorly suited to macro-image recording. Since conventional silver halide recording elements, such as micro-films, record both micro-images and macro-images at almost identical contrasts, the same high contrast that is optimum for micro-image recording must be tolerated for macro-image recording. A common result is microfilm records in which the fine-line copy appears sharp and well defined, but the continuous tone large area uniform tone areas appear too high in contrast and lack shadow detail.
U.S. Pat. No. 3,615,499 of Groet, issued Oct. 26, 1971, describes a photographic process which produces high contrast images of fine line copy and improved continuous tone images. The process comprises developing, with a primary aromatic color developing agent, an imagewise exposed photographic element comprising a support having coated thereon a photographic silver halide emulsion layer containing a development inhibitor releasing coupler, in the presence of a competing coupler which produces substantially no permanent dye in the emulsion layer and a silver halide solvent.
In Defensive Publication T904,022 of Kurz et al, it is disclosed that photographic images of increased sharpness can be obtained by incorporating physical development inhibitors in silver halide emulsions and developing them with silver solvents after exposure.
Surface fogged silver halide grains have been incorporated in silver halide emulsion layers of color photographic elements for the purpose of enhancing favorable interimage effects. Groet, in commonly assigned U.S. Application Ser. No. 688,445, filed May 20, 1976 now U.S. Pat. No. 4,082,553, issued Apr. 4, 1978, discloses a photographic element capable of producing multicolor dye images upon reversal processing. At least two silver halide emulsion layers are provided, each primarily responsive to a different region of the spectrum. In one of the emulsion layers the light-sensitive silver halide is silver haloiodide and in an adjacent emulsion layer surface fogged silver halide grains are blended. In a preferred form three silver halide emulsion layers are provided, each responsive to a different one of the blue, green and red regions of the spectrum and each containing light-sensitive silver haloiodide grains and surface fogged silver halide grains. It is, of course, essential that adjacent emulsion layers be responsive to a different portion of the spectrum in order for a favorable interimage effect to be obtained.